Thornton, Frank (1891–1965), revolutionary and company director, was born 12 April 1891 in Peter Street, eldest of three sons and five daughters of Hugh Thornton, housepainter, and his wife Mary (née Harte), both of Drogheda, Co. Louth. He was educated at St Joseph's CBS, Sundays Gate, Drogheda. In December 1912, on the closure of his father's business, he emigrated with his family to Liverpool, where he joined both the Gaelic League and the IRB. He subsequently joined the Irish Volunteers at Duke St., Liverpool, and became captain of B Company in 1914. He was officer in charge of the guard of honour when the body of Jeremiah O'Donovan Rossa (qv) arrived in Liverpool from America en route to Ireland in July 1915 and he escorted the remains to Ireland.
In January 1916, he travelled to Dublin with B Company and went into a training camp at Kimmage. The following month he was sent as staff officer to Limerick city Volunteers, but in March was ordered back to Dublin. He took part in the Easter Rising, firstly as captain in charge at Liberty Hall on Easter Monday, later moving to take charge of the Imperial Hotel on O'Connell Street. He was wounded twice during the rebellion. After the surrender he gave his name in Irish, Prionsias Ó Droighneáin. When the arresting officer translated this into English as Frank Drennan, Thornton concurred, and under this name he was sentenced to death; this was subsequently commuted to ten years penal servitude. Incarcerated in Dartmoor and Portland prisons, he was released in the general amnesty of 1917. Rearrested the same year, he went on hunger strike on two occasions in Dundalk and Belfast gaols, and during the ‘German Plot’ scare of May 1918, he was incarcerated in Reading jail. Released in 1919, he served on the organisation staff of General Headquarters, in which he played a major role in organising the IRA in Louth, Monaghan, Cavan and Longford. He was then appointed sub-director of Intelligence by Michael Collins (qv), of whom he was a great admirer and whom he had first met in Liverpool in 1913. He took an active role in gathering intelligence and other clandestine operations during the war of independence.
He supported the Anglo-Irish treaty of December 1921, and the following year joined the new army with the rank of colonel commandant and was in charge at Oriel House. During the civil war he was badly wounded outside Carlow, allegedly while hunting for Éamon de Valera (qv). He remained in the army until 1924 when he resigned at the time of the army mutiny. He returned to the army during the Emergency (1939–45), serving as a captain in the 26th Battalion. After the Emergency he was appointed life president of the 2nd Battalion, Old IRA, Dublin Brigade.
One of the founders in 1918, with among others James Ryan (qv), of the New Ireland Assurance Company (apparently the idea was conceived in prison), he was successively assistant manager (1924), manager (1954) and general manager (1959). He was a life long member of the GAA until his death on holiday in Sitges, Spain on 22 September 1965. His funeral attendance included Éamon de Valera and Seán Lemass (qv). In 1934 he married Mary (née Mulhall); they lived at St Helen's Road, Booterstown, and had a son Pádraig. Correspondence from Frank Thornton is in the papers of Piaras Béaslaí (qv) in NLI (see NLI, collection list no. 44).